In the EV Outlook Client trace you very often see the Connection Status listed as a number.. well, what does the number mean ?

0 = Unknown connection. You sometimes see that near the start of a client trace.

1 = Online

2 = Offline

3 = No Exchange

4 = Disconnected

5 = Cached Mode, Offline

6 = Cached Mode, Disconnected

7 = Cached Connected, headers only

8 = Cached Connected, Full items

9 = Cached Connected, “Drizzle Mode”

These are of course the Outlook to Exchange connection states, and the EV Outlook Add-in often needs to know what state things are in so that various operations can be performed (or not as the case may be).